Speaking in Brussels, Obama suggested that further U.S. and Western sanctions against Russia could be forthcoming, even without additional provocation from Russian President Vladimir Putin.

Using rather dramatic language, Obama said the world had entered "a global moment of testing," and he implored Europe to recommit to freedom and human dignity saying, "If the Russian leadership stays on its current course, together we will ensure that this isolation deepens."

Saul Loeb | AFP | Getty Images

President Barack Obama delivers a speech at the Palais des Beaux-Arts in Brussels on March 26, 2014.

Cramer fully understands that Wall Street was not on the president's mind as he made these comments. Nonetheless, "his words scared the heck out of buyers. That's why the stock market reversed to close lower," Cramer said.

Therefore, if you're an investor, you have to assume the market landscape has been altered, at least for a while. Nothing else would be prudent.

Reflecting on the potential ripple, Cramer said, "His comments made me think that some of our more international companies should expect some hardship as we're going to try to put through sanctions. And, as a result, if sanctions call global growth into question, industrials may be challenged."

And it's not just U.S.-based firms that could take a hit.

"I'm hearing that German Chancellor Angela Merkel has canvassed German companies to see if they would be up for strict sanctions even if it hurt business, and reports are that they said it's important to protect Ukrainian sovereignty. So, the answer is yes."

That's not to say the stock market won't rally again. The Dow Jones industrial average and S&P 500 could rally in a heartbeat if geo-political issues ease. Or, as the market grows comfortable with sanctions, earnings and M&A could drive a rally.

But right now, it appears Ukraine is again moving front and center, and Cramer wants investors to be prepared.

"President Obama's commentary created a new level of uncertainty," he said. And if the market hates anything, it's uncertainty.